Art of refining



Patented Nov. 15, 1938 ART OF REFINING Matthew Fairlie, Hammond, Ind.. assignor to Sinclair Refining Company, New York, N. Y., a corporation of Maine No Drawing. Application May 5, 1936,

Serial No. 77,923 i 2 Claims. (Cl: 879) This invention relates to improvements in petroleum hydrocarbon oils. More particularly, it relates to inhibition of oxidation in petroleum oils, lubricating oils in particular, having a Saybolt Universal viscosity upwards of seconds at 100 F. by the addition thereto of an organic oxidation inhibitor. The invention includes a new organic oxidation inhibitor and an improved compounded petroleum oil containing the new oxidation inhibitor of the invention.

Petroleum oils have a tendency to form sludge and gummy and resinous substances. The formation of these substances isgenerally objectionable, particularly so where it is desired to maintain the oil in a continuously uniform condition. One generally accepted explanation assumes that the formation of these substances results from oxidation. Whatever may be the true explanation, it is known that when lubricating oils are used in internal combustion engines, for example, these undesirable substances form and, as formed, are commonly referred to as sludge.

Sludge may appear in a variety of forms ranga ing from deposits quite soft and gelatinous in the respects noted, causes an increase in viscosity accompanied by an increase in the variability of viscosity with changing temperature. Where the maintenance of continuously uniform properties is desirable, such changes are, of course, objectionable.

In accordance with the present invention, sludge formation and such changes with respect to viscosity are inhibited, thereby promoting uniformity of properties and increasing the useful life of the oil, the period over which those properties remain within limits appropriate to the particular use.

It is an object of the present invention to provide an oxidation inhibitor which when incorporated in petroleum oils in proper proportion will minimize or inhibit oxidation of the oil. A further object of the invention is to provide a compounded petroleum oil containing the new inhibitor of the invention which has greatly reduced tendencies to form sludge and similar oxidation products. A still further object is to provide an oxidation inhibitor which when incorporated in a petroleum oii, as defined herein, will inhibit oxidation and reduce the tendency of the oil to undergo changes with respect to viscosity.

I have discovered that quinaldine (alpha methyl quinoline) C9HsN-CH3,

exhibits excellent oxidation inhibiting properties. When added to petroleum oils, having a Saybolt Universal viscosity upwards of 50 seconds at 100 F., in amount approximating 0.5% by weight, for example, oxidation with its resultant sludge formation is markedly inhibited and changes with respect to viscosity are retarded.

It might be noted that extensive investigations have shown that substances known to be oxidation inhibitors in arts otherthan the petroleum art have little or no value as applied to petroleum oils. In a number of instances tests have shown that some of these known oxidation inhibitors were detrimental when incorporated in petroleum oil and actually. caused an increase in the rate of sludge formation.

As the value of an oil which is to be used over and over again, or subjected to continuous use, forexample, depends largely upon its stability,

tests have been devised to determine the stability of an oil in particular respects. Thus tests have been developed which enable one to determine to what extent an oil will sludge when in use, and these tests furnish a means for evaluating the oil in this respect and to determine the efliciency of oxidation or sludge inhibitors. One of these tests is known as the Indiana oxidation test. This test is described in an article entitled Causes and effects of sludge formation in motor oil appearing on pages 167, 168 and 181 of the Journal .of the Society of Automotive Engineers for May, 1934,,where the problem of sludge formation is treated at considerable length. This Indiana oxidation test, to which reference is made hereinafter, ofiers a means of determining the so-called sludging time of an oil.

In this test 300 cc. of the oil to be tested are placed in a glass tube twenty inches long by one and three-quarter inch internal diameter, secured in an oil bath maintained at a temperature sufiicient to keep the test oil at 341 F. The level of the oil in the tube should be well below the bath level. Air is passed through the oil, being introduced througha glass tube of threesixteenth inch internal diameter at a point about one-quarter inch from the bottom of the glass tube at a rate of ten liters per hour. Periodically, depending on the oxidation characteristics of the oil, 25 cc. of oil are removed, 10 grams of which are immediately weighed into a tarred Erlenmeyer flask. This. portion is diluted with 100cc. AQS. T. M. precipitationnaphtha and allowed to stand three hours before filtering through a Gooch crucible. Th crucible containing the insolubles is washe with approximately 100 cc. of naphtha after which it'is dried one-half hour at 300 F. and weighed. The amount of insoluble matter is expressed in milligrams per ten grams of oil. A- sufficient number of samples should be taken for test to determine accurately the sludging time, that is, the time required to form ten milligrams of naphtha insoluble matter per ten grams of oil. When employing the above test it is common to also determine the 100 milligram point, i. e., the time to form 100 milligrams of insolubles, but it will be understood that the sludging time is the time required to form 10 milligrams of naphtha insoluble material per 10 grams of oil.

The determination of viscosity increase, which becomes the more'important criterion when the sludging time 'is much over 50 hours, is made by taking a 100 cc. sample every 50 hours.

sample is promptly run for viscosity and put This back in the oxidation tubes. Oxidation tests are ordinarily continued either to the 100 miligram point or for 150 to 200 hours for so-called sludgeless oils.

The following example will illustrate the-in- 'vention:

0.50 percent by weight of quinaldineis added to an oil having an Indiana sludging time of 21 hours and a viscosity rise of 9.50 seconds (Saybolt Universal) at 210 F. after 50 hours. Upon test the oil, with added quinaldine, was found to have an Indiana sludging time" of 47 hours and a viscosity rise of 1.3 seconds (Saybolt Uni-' versal) at 210 F. after 50 hours.

The oil employed in the foregoing example was of Mid-Continent base and, had the following characteristics: 1

Gravity A. P. I 24.8 Viscosity at 100 F.

' (Saybolt Universal) 513 Viscosity at 210 F. f Y (Saybolt Universal)" 60.6

Viscosity index 79.2 Flash point F 435 Fire point F '500 Pour oint. F 0 Acid number; .025 Iodine number '20.2 Aniline point"; -C 97.5'

The proportion of quinaldine to. be incorpouse, as opposed to petroleum oils which are immediately consumed in use, and it is in this connection that the invention has its greatest utility. Where oil is to be consumed, burned for heating purposes in an oil heater, for example, the invention is not of equal importance as when the oil is being used over and over again, since utilization of an oil for burning involving destruction of the oil is inconsistent with its preservation for re-use.

Again, for such purpose it is of less consequence that the oil have'highresistance to sludge formation and changes with respect to viscosity since the oil is being subjected to a use where these properties are of secondary importance. In either case, however, the addition of the oxidation inhibitor of the invention, in proper proportion, will inhibit sludge formation and retard changes with respect to viscosity, but its utility in one case is greater than in the other.

The terms oxidation inhibitor and oxidation as used herein and in the claims are intended to be used in their broad rather than their narrow sense. Oxidation is intended to refer to themanner of formation of the undesirable substances in the oil, regardless of the precise manner of their formation. The inhibitor employed to retard or limit the formation of .these undesirable substances has been termed an oxidation-inhibitor in the same sense.

I I claim: a

1. A petroleum lubricating oil having a Saybolt Universal viscosity upwards of 50 seconds at 110 F. containing about 0.5% by weight of quinaldine to inhibit oxidation of the oil up to temperatures to which the oil will be raised during lubricationof an internal combustion engine. 

